5. Foetopathy of swine caused by parvoviruses (SMEDI).

Question 1

SMEDI VIRUS INFO?

Answer 1

• 18-26nm diameter
• Icosahedral shape
• non-enveloped
• resistance = very strong
• infectious for month in the environment
• Single strand, linear DNA genome (4-6kb) a bit larger than the circovirus
• 2-5 structural proteins & a few proteins to help the replication (helper virus: Adeno or Herpes or
• another bigger virus with polymerase enzyme)
• Haemagglutination - Haemaglutin protein
• Uses cellular polymerase enzyme: replication in dividing cells or usage of helper viruses
• Good antigen
• Stenoxen: so can find everywhere in the world
• Parvovirinae subfamily ʹ- the taxonomy is quite outdated… the name has changed

Question 2

Subfamily = Parvovirinae?

Answer 2

Subfamily = Parvovirinae

• Aveparvovirus: Chicken parvovirus (Galliform aveparvovirus 1) ChPV
• Protoparvovirus
• Carnivore protoparvovirus 1: Feline panleukopenia virus FPV, Canine parvovirus
• 2 CaPV, Mink enteritis virus MPV, Racoon parvovirus
• Porcine parvovirus (Ungulate protoparvovirus 1) PPV1 Etc
• Erythroparvovirus: Human parvovirus B19 (Primate erythroparvovirus 1) HPV, Bovine
• parvovirus type 3 (Ungulate erythroparvovirus 1) BPV
• Dependoparvovirus: Adeno associated virus (Adeno-associated dependoparvovirus) AAV,
• Goose parvovirus (Anseriform dependoparvovirus 1) GPV, Duck parvovirus (Anseriform
• dependoparvovirus 1) DPV Etc
• Amdoparvovirus: Aleutian mink disease (Carnivore amdoparvovirus 1) AMDV
• Bocaparvovirus: Bovine parvovirus (Ungulate bocaparvovirus 1) BBoV, Human bocaviruses
• (Primate bocaparvovirus 1, 2) HBoV, Canine minute virus (Carnivore bocaparvovirus 1)
• CaBoV, Porcine bocaviruses (Ungulate bocaparvovirus 2-6) PBoV
• Copiparvovirus: Ungulate copiparvovirus 1-2 (PPV-4)
• Tetraparvovirus Ungulate tetraparvovirus 1-4 (Hokovirus, PPV-3)
• Subfamily = Densovirinae: Densovirus, Iteravirus, Brevidensovirus, Pefudensovirus

Question 3

PPV1 history?

Answer 3

Porcine parvovirus disease (PPV1)

• History:
• 1965: Dunne, SMEDI (Stillbirth, Mummification, Embryonic Death, Infertility)
• clinical signs of pigs
• 1967: not enterovirus but parvovirus

Question 4

Prevalence and PPV aetiology?

Answer 4

Prevalence:

• everywhere, wherever pigs are present,
• less frequent in Australia & New Zealand

PPV aetiology

• Uses cellular polymerase enzyme: replicates in dividing cells
• Good antigens
• 2 genes
• 3 structural proteins: VP1, VP2 Neutralising epitopes, VP3

Question 5

Pathogenesis?

Answer 5

Pathogenesis:

• Viral intake PO
• viral replication: lymphoid tissues around throat & small intestine
• (dividing cells)
• viremia (transient, symptomless) 1-7 days Foetus across the placenta (2 weeks after the infection) (dividing cells)

Question 6

Replication?

Answer 6

Replication:

• Macrophages (& monocytes) are passed to the foetus
• Cannot cross the placenta in seropositive sows
• Maternal immunity protects up to 6 months
• Antibodies appear in the 2nd-6th days,
• the max level of the antibodies production is
• on the 14th day & the production lasts for 9-10 months

Question 7

5 biotypes

Answer 7

5 biotypes:

• 1) NADL-2: apatogen
• 2) Classical PPV1: in susceptible sows SMEDI
• 3) kresses strain dermatitis immunocompetent foetus dies
• 4) Strain with skin symptoms
• 5) Co-infection with PCV-2: PMWS or PRDC

Question 8

Intake?

Answer 8

• Intake: PO/another route e.g. aerogenic route
• Spreading via:
• faeces, saliva
• infected objects (fomites), wind
• survives minimum 4 months
• boar (infected semen)

Question 9

Clinical signs?

Answer 9

Question 10

Pathology?

Answer 10

Pathology

• Not uniquely characteristic to PPV1 (unlike PCV 2)
• Foetal development disorders
• Piglets in different stages on infection
• Subcutaneous haemorrhage
• Mummification
• Effusion (sera, blood)
• Enlarge liver & kidney

Question 11

Histopathology?

Answer 11

Histopathology (foetus)

• Not uniquely characteristic to PPV1
• Lymphoid infiltration & calcification in the placenta
• Hepatitis, nephritis, perivascular mononuclear infiltration in the brain
• Increased lymphocytes (plasma cells), monocytes, macrophages, dendritic cells

Question 12

Diagnostics?

Answer 12

Diagnostics

• Serology: VN: CPE, cell death after inoculation 2-8 days (neutralisation atg: VP2)
• If more than 258
• IF
• HAI (haemagglutination inhibition) (mix serum of sheep, guinea pig, rat, chicken RBCs with virus, and if enough antibodies will hemagglutinise)
• ELISA
• Direct virus detection: IF (tissue section),PCR, HA (tissue homogenates),
• virus isolation (CPE)

Question 13

Differentiation?

Answer 13

Differentiation:

1. PRRS,
2. PCV2,
3. Leptospirosis,
4. Brucellosis,
5. CSF/ASF͕,
6. aujeszky disease,
7. FMD

Question 14

Vaccines?

Answer 14

Vaccines:

• Protection:
• Natural seroconversion
• Vaccination after 6 months of age
• 1x or 2x before breeding
• Repeat 1x every year
• Inactivated (live), monovalent, combined
• Emerging porcine parvoviruses
• Originally 1 serotype (PPV1): SMEDI Now PPV2-6